1. Field of the Invention
The present invention relates to the conversion of the size of hydrocarbon molecules in a process stream, using an electrical method, and can be used either to combine small molecules into larger molecules or to separate larger molecules into smaller molecules.
2. Description of Prior Art
In the petroleum process industries, for many decades a thermal separation process has been applied to crude oil, which is a mixture of hydrocarbons, to separate out various fractions which are subsequently used for specific purposes. For example, diesel fuel, gasoline, lubricating oils, and asphalts are separated by vaporization and subsequent condensation at appropriate different temperatures and heights in a tower. The resulting yields of refined products are dependent upon the characteristics of the crude oil supplied, which will be different for each petroleum reservoir. The market demand for each category of refined products is variable in time, and therefore the adjustment of the petroleum refining process to changes in input composition and output demand can be difficult and challenging.
One remedy which has been recognized for many years is to convert larger molecules into smaller ones, a process called cracking, which has been normally accomplished by catalytic action on special surfaces at high temperatures. In this way, for example, an extra quantity of heavy oils can be converted into gasoline, which may be more marketable. Limitations of this approach include the cost of catalysts, the range of input molecules for which they are effective, and the thermal energy required for the process, which is difficult to recover.
On the other hand, the world supply of liquid hydrocarbons is also being consumed, and within only a few decades the known reserves will be exhausted. Two obvious alternatives involve the utilization of other natural sources of hydrocarbons which are in abundant supply: natural gas, and heavy oil. Keeping in mind that the majority of uses of petroleum in equipment use in our era have been for fuels in liquid form (such as gasoline, diesel fuel, jet fuel, and the like), and the transport of liquid fuel at normal atmospheric temperature and pressure is a decided advantage and has been designed into equipment in use today, it is clear that an important advantage would be derived from methods to convert natural gas (typically methane and ethane, CH.sub.4 and C.sub.2 H.sub.6) into liquids (C.sub.4 H.sub.x to C.sub.10 H.sub.y, for example). Natural gas is easily withdrawn from reservoirs, and, if converted into higher molecular weight species, could readily be transported from remote source locations to consumers via existing liquid petroleum pipelines or ships, whereas in it's natural gaseous form or refrigerated liquid form, special-purpose pipelines and ships must be constructed, and the use of natural gas as a vehicle fuel by the consumer would require substantial investment in new equipment on vehicles. A process has in fact been built and operated commercially by the New Zealand government which produces some 14,450 barrels of gasoline per day using natural gas as a feedstock. It is a three stage process; the first producing hydrogen and carbon monoxide, the second producing methanol, and the third producing gasoline via the Mobil MTG (methanol-to-gasoline) process which uses a synthetic zeolite catalyst ZSM-5 (U.S. Pat. No. 3,702,886, Argauer and Landolt). The incorporation of zeolites into various reactor geometries is considered in U.S. Pat. Nos. 4,058,576 (Chang and Grover), U.S. Pat. No. 3,928,483 (Chang, Silvestri, and Smith), U.S. Pat. No. 3,931,349 (Kuo), U.S. Pat. No. 4,138,440 (Chang, Jacob, Silvestri, and Zahner), U.S. Pat. No. 4,197,418 (Lee and Yurchak), U.S. Pat. No. 4,046,825 (Owen and Venuto), and U.S. Pat. No. 4,251,484 (Daviduk and Haddad). Two difficulties with all of the processes based upon these patents are, firstly, that a multi-stage conversion process from natural gas to gasoline is involved, and, secondly, that high operating temperatures are involved (315 degrees C. to 450 degrees C.). Both difficulties lead to loss of energy and to high cost of initial equipment. An approach which involves a single-stage direct conversion, and in which the energy which is to be supplied to the reaction is specifically used to accomplish the molecular conversion, with a minimum waste as heat, would represent an improvement. Furthermore, the MTG process is limited as to the size of large molecules which may be formed, by the interior dimensions of the columns of the synthetic zeolite molecule. A process which allows the combination of molecules with virtually unlimited larger sizes would have additional uses in the production of lubricating oils and heavier fluids. The principle of molecular conversion thus has wide application.
Although the foregoing discussion of molecular conversion is oriented towards hydrocarbon gaseous-to-liquid conversion, it is obvious that compound gases containing other elements, such as oxygen, chlorine, flourine, bromine, nitrogen, sulfur, hydrogen, silicon, and other elements could be changed in composition in order to accomplish certain benefits, such as the diminution of toxicity prior to release into the natural environment, or the alteration of composition so as to render harmful gases into harmless liquids or gases prior to release into the environment. The chloroflourocarbon gases, for example, which interact with naturally-available ultraviolet radiation when they are present in the atmosphere, could be transformed into liquid forms in combination with other elements which would be relatively harmless. Accordingly, it is the object of this invention to provide an electrical device which will accomplish the function of combining molecules of low molecular weight into molecules of higher molecular weight. A further object of the invention is to provide an electrical device for separating molecules of higher molecular weight into other molecules of lower molecular weight. Moreover, an additional object of the invention is to provide an electrical device for combining two or more different molecular species into new molecular species.